Patent GB-1231900-A (GB)
IPC: F16H61/02
Filed: 1968-12-27
Abstract: 1,231,900. Slides. C. R. LAPPAGE. 26 March, 1970 [27 Dec., 1968], No. 61528/68. Heading B3B. Selective ball clutches 67, 76, for high and low speed (or reverse) traverse drive of a lead-screw 18, traversing, through a nut 17, a table 10 of a machine-tool, are controlled by axial movement of a coaxial shaft 34, induced by end-thrust on a helical gear pair (32), 33 driving the shaft. The two speeds may be obtained by separate motors, but, as shown, a single motor (13, Fig. 1, not shown) drives the lead-screw 18 through the helical pair (32), 33 for high speed, and through a pick-off gear pair (47, 46, Figs. 3 and 5, not shown), worm (42) and worm-wheel 38 for the much slower low speed. The helical wheel 33 meshes a further helical wheel carrying a drag-brake (50, Fig. 3, not shown), applying a permanent load to the wheel 33 so that endthrust in the appropriate direction is always acting on the shaft 34. Positive clutches.-The ball selector clutches 67, 76 connect an axially-fixed driven sleeve 36, dog-coupled at 19 to the output lead-screw 18, either to the slowly-driven worm-wheel 38 for low speed or to the axially-movable fast-driven shaft 34 for high speed, under selective control by axial movement of the shaft 34, controlled by the machine table 10 reaching pre-set points in its axial travel. In the position shown in Fig. 4, the balls 76, carried in radial slots 77 in the driven sleeve 36, engage notches in a collar 74 on the shaft 34, thereby clutching the shaft 34 to the sleeve 36 for high speed. Leftward axial movement of the shaft 34 disengages the balls 76 from the notches in the collar 74, releasing the high-speed clutch, and causes a coned surface 64 of a sleeve 63, axially secured to the shaft 34, to project balls 67 in shaft slots 66 radially outwards into engagement with crescent grooves 69, Fig. 9 (not shown), in a collar 68, secured to the worm 38, thereby clutching the worm 38 to the shaft 34 for low speed. Shift control.-The traverse-controlled axial positioning of the shaft 34, for ratio-shift, is governed by three pins. One, 88, Fig. 7 (not shown), permanently fixed, engages a groove 84, Fig. 8, closed at its right end, on one side of a bearing collar 80 sliding axially with the shaft 34, and hence limiting leftward movement. Two pins 89, 97, Fig. 2, controlled through rockshafts 91, 100 by trip surfaces 105, 106 on the machine, engage aligned grooves 83, 85 in the other side of the collar 80 to prevent rightward and leftward movement respectively. Control is as follows: Starting from the Fig. 1 position with the table 10 at the right side and the high-speed ball-clutch 76 engaged, leftward movement of the control shaft 34, under helical gear thrust, is prevented by the pin 89 in the collar groove 83, so that the table is traversed left at high speed until, e.g. the table reaches the work, when the trip surface 105 withdraws the pin 89 from the groove 83, allowing the control shaft 34 to move left united by the fixed pin (88), under axial gear-thrust, disengaging the high-speed ball-clutch 76 and engaging the low 67. As soon as the trip-surface 105 is passed, the pin 89 is released and now engages the other collar-groove 85, preventing rightward movement of the control shaft 34. Traverse continues at low speed to the end of the work, as determined by an adjustable stop (116, Fig. 1, not shown), which detains the table 10, but the lead-screw 18, still driven, then moves axially to the left, in opposition to disc springs (25, Fig. 1, not shown), to operate, through a fork 109, a motor reversing switch for return traverse. On the return stroke, low speed persists until the trip surface 105 releases the pin 89, whereupon the gear-thrust, now rightward, shifts the control shaft 34 to the right until arrested by the pin 97, thus shifting to high speed, which persists until, at the return datum end of the travel, the fixed surface 104 releases the pin 97 and allows the control-shaft 34 to move further right to a neutral position with both clutches disengaged. The machine is then ready for another traverse, started by manually or automatically reversing the motor, which causes leftward movement of the control shaft 34 until detained by the pin 89 in the high-speed position. Additional traverse speeds may be obtained by using a two-speed motor.